Engines may include crankcase ventilation systems to vent gases out of the crankcase and into an engine intake manifold to provide continual evacuation of gases from inside the crankcase in order to reduce degradation of various engine components in the crankcase.
Under certain conditions, crankcase ventilation systems may be monitored to identify breaches in the system. For example, a fresh air hose (breather tube) may become disconnected, an oil cap may be off or loose, a dipstick may be out, and/or other seals in the crankcase ventilation system are broken then degradation of various components included in the crankcase may occur.
Diagnostic blowby approaches may be used to monitor crankcase ventilation system integrity. For example, a pressure sensor may be used in the crankcase and a valve in a PCV fresh air hose may be opened so that pressure or vacuum changes may be sensed in the crankcase to determine if there is a breach in the system.
In other approaches, a plurality of absolute sensors, e.g., a barometric pressure sensor (BP), a compressor inlet pressure sensor (CIP), a throttle inlet pressure sensor (TIP), a manifold air pressure sensor (MAP), and/or a pressure sensor in a crankcase vent hose, etc., may be used in combination to monitor crankcase ventilation system integrity.
However, the inventors herein have recognized that such approaches may add additional hardware to such monitoring systems, e.g., additional sensors and valves, thus increasing costs and complexity of a crankcase ventilation monitoring system. For example, a compressor inlet and a crankcase vent tube may read substantially the same pressure under certain conditions; thus, including sensors in both the PCV breather tube and at the compressor inlet may not be needed when used in combination with a barometric pressure sensor during crankcase ventilation system diagnostic routines.
Thus, in one approach, to at least partially address these issues, a method for monitoring crankcase ventilation system integrity is provided. The method comprises indicating a crankcase ventilation system degradation based on a lower vacuum than expected downstream in a crankcase vent tube or in the main engine air duct to with the crankcase vent tube attaches. For example, indicating a crankcase ventilation system degradation based on a lower vacuum than expected downstream of a crankcase vent tube may include indicating a crankcase ventilation system degradation based on an absolute pressure sensor measurement relative to a gauge pressure sensor measurement.
In this way, the number of sensors and valves employed in a crankcase ventilation monitoring system may potentially be reduced, leading to a reduction in cost and complexity in a crankcase ventilation monitoring system. Further, in such an approach, the crankcase ventilation system may remain active during a diagnostic procedure.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.